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Other authors have already shown MRI used early to investigate clinical scaphoid fracture (patients with clinically suspected scaphoid fracture with normal initial plain films) to have excellent sensitivity and specificity when compared with plain films delayed up to 6 weeks. MRI in this setting has also been shown to be extremely reliable.
We felt it was unnecessary to duplicate this work. There are no data on delayed radiographs in our study population because they only had MRI. Our discussion of a gold standard was intended to collate the information from various studies and thereby justify our approach of using MRI as the sole investigation in this group of patients—a radical departure from standard practice.
The clinical and radiological issue is that in scaphoid trauma, radiographs cannot exclude a fracture until 6 weeks. In addition to the insensitivity issue, plain films have been shown to suffer from poor reliability at 1 day, 2 weeks and 6 weeks post injury, calling their use into question. The challenge is to find an alternative investigation that can make an accurate positive or negative diagnosis as early in the post injury phase as possible to avoid overtreating the majority of patients with negative initial films.
The issue with bone scintigraphy in clinical scaphoid fracture is poor specificity. At no point did we state that bone scintigraphy had higher sensitivity for fracture than delayed radiographs—in the two studies cited [1, 2], delayed radiographs were used as the gold standard which makes it impossible to come to that conclusion. That scintigraphy is more sensitive than initial radiographs is a given.
MRI has both high sensitivity and specificity when compared with delayed radiographs. As with scintigraphy, delayed radiographs were used as the gold standard in these studies therefore it is impossible to conclude that MRI is more sensitive than delayed radiographs. In our view MRI is a better investigation than bone scintigraphy because it is more specific for fracture than scintigraphy. MRI is also extremely reliable: the combination of high sensitivity, specificity and reliability make it a very robust investigation that is able to make an accurate positive or negative diagnosis very early in the post injury phase.
In our study population of clinical scaphoid fracture patients, using MRI as the sole investigation management was changed in 92% [3]. This is beneficial to the patient and to the health service.
Crowds tend to gather around street magicians to see what is going on. If our paper has a similar effect we would be delighted. We believe that the evidence is robust, the arguments are balanced and the potential benefits from a change to this practice are great. The wider an audience that is reached the better.
Yours etc.,
Department of Radiology, Western Infirmary, Dumbarton Road, Glasgow, G11 6NT, UK
Received for publication August 20, 2003. Accepted for publication September 10, 2003.
References
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